Scott: Street and Performance DID have the mounts for an LS series engine into an AD truck!
Apparently, you use the Chassis Engineering small block mounts, plus LS engine adaptors. They also offered me a crossmember for the 700R4 tranny.
About $300 total, no design work required, and the whole setup BOLTS - not welds - right in! To top it all off, "Mark", the technical guy who equipped me with all this, HAS an LS engien in his own personal 1958 Chevy pickup.
Street and Performance lived up to its reputation!
Jim G